Surface mount technology involves attaching electronic components directly to the surface of printed circuit boards, as opposed to through-hole technology where components are inserted into holes. There are three main types of surface mount assemblies depending on whether components are mounted on one or both sides of the board. The surface mount process involves designing the board, applying solder paste, placing components, soldering, cleaning, and potential repair. Infrared and hot gas soldering are two common soldering techniques used. Reworking involves removing faulty components and soldering new ones in their place.

1. BY
S.NAVYA PRAVALIKA
AND
M.L .SINDHURI

2. A method of assembling printed wiring
boards or hybrid circuits, where
components are attached to pads on the
board surface, as distinct from through-hole
technology, where component leads are
inserted into holes.

3. There are 3 major types of Surface Mount Assemblies:
 Type I
(Full SMT board with parts on one or both sides of the
board)
 Type II
(Surface mount chip components are located on the
secondary side of the Printed Board (PB). Active SMCs
and DIPs are then found on the primary side)
 Type III
(They use passive chip SMCs on the secondary side, but
on the primary side only DIPs are used)

4. •SURFACE MOUNT DESIGN
•SOLDER PASTE APPLICATION
•COMPONENT PLACEMENT
•SOLDERING
•CLEANING
•REPAIR/REWORK

5. SURFACE MOUNT DESIGN

6. It depends on a number of factors
• Market needs
• Function
• Package moisture sensitivity
• Thermal and solder joints reliability
• As the packaging density increases, thermal problems are
compounded, with a potential adverse impact on overall
product reliability

8. Feed mechanism used to load components
into a pick-and-place machine
SMD pick-and-place machine (with
simulated motion blurs)

9.  Soldering is a process
in which two or more
metal items are joined
together by melting
and flowing a filler
metal into the joint, the
filler metal having a
relatively low melting
point.

10.  INFRARED SOLDERING
 CONVENTIONAL HOT GAS SOLDERING

12. ADVANTAGES
•Easy setup
•No compressed air
required
•No component-specific
nozzles (low costs)
•Fast reaction of infrared
source
DISADVANTAGES
•Central areas will be heated more
than peripheral areas
•Temperature can hardly be
controlled, peaks cannot be ruled out
•Covering of the neighboured
components is necessary to prevent
damage, which requires additional
time for every board
•Surface temperature depends on the
component's reflection
characteristics: dark surfaces will be
heated more than lighter surfaces

13. During hot gas soldering, the energy for heating up the
solder joint will be transmitted by a gaseous medium. This can be
air or inert gas (nitrogen)

14. ADVANTAGES
•Simulating reflow oven
atmosphere
•Switching between hot gas and
nitrogen (economic use)
•Standard and component-
specific nozzles allow high
reliability and reduced process
time
•Allow reproducible soldering
profiles
DISADVANTAGES
•Thermal capacity of the heat
generator results in slow reaction
whereby thermal profiles can be
distorted
•A rework process usually
undergoes some type of error, either
human or machine-generated, and
includes the following steps:
1. Melt solder and component
removal
2. Residual solder removal
3. Printing of solder paste on PCB,
direct component printing or
dispensing
4. Placement and reflow of new
component

15. •A specially formulated alloy in wire form is
designed to melt at the low temperature of around
136 degrees F, 58 degrees C. It eliminates the
potential for damage to the circuit, adjacent
components, and the device itself.
•Liquid flux and a soldering iron are used to melt
this low temperature alloy that is specially
formulated to stay molten long enough to react with
existing solder. The SMT device can then be easily
removed with a vacuum pen

16. Apply Low Residue Flux to all the leads
on the SMD you're removing

17. With a soldering iron, melt the low
temperature alloy

18. Easily lift device off the board with a
vacuum pen

19. •Finally, the boards are visually inspected for
missing or misaligned components and solder
bridging.
•If needed, they are sent to a rework station where
a human operator corrects any errors.
• They are then sent to the testing stations to
verify that they operate correctly.

20. Thoroughly clean site and solder new
device to PBC

21. •Smaller components. Smallest is currently 0.4 x 0.2 mm.
•Much higher number of components and many more connections per
component.
•Fewer holes need to be drilled through abrasive boards.
Simpler automated assembly.
•Small errors in component placement are corrected automatically (the surface
tension of the molten solder pulls the component into alignment with the solder
pads).
•Components can be placed on both sides of the circuit board.
•Lower resistance and inductance at the connection (leading to better
performance for high frequency parts).
•Better mechanical performance under shake and vibration conditions.
•SMT parts generally cost less than through-hole parts.

22. •The manufacturing processes for SMT are much more
sophisticated than through-hole boards, raising the
initial cost and time of setting up for production.
•Manual prototype assembly or component-level repair
is more difficult given the very small sizes of many
SMDs.
•SMDs can't be used with breadboards , requiring a
custom PCB for every prototype. The PCB costs dozens
to hundreds of dollars to fabricate and must be
designed with specialized software.
•SMDs' solder connections may be damaged by potting
compounds going through thermal cycling.